Shaping molds for producing filmlike articles

ABSTRACT

A shaping mold for producing filmlike articles by the fluidization process, this mold consisting of a completely closed enclosure formed in a metallic material having good heatconducting properties but a reduced thickness. The enclosure communicates with the surrounding free atmosphere, during the heating thereof, via at least one tube carried by an opening into a portion of the enclosure which does not partake in the shaping of any portion of the filmlike article.

United States Patent Giifard et al.

[45] Feb. 8, 1972 [54] SHAPING MOLDS FOR PRODUCING FILMLIKE ARTICLES[72] Inventors: Louis Gifiard, rue Houvenagle, Saint Brieuc, Cote duNord 5; Jean Fougeray, rue Charles Floquet, rueil Malmaison, Hauts deSeine 21, both of France [22] Filed: Oct. 15, 1969 [21] Appl.No.:866,466

[30] Foreign Application Priority Data Nov. 4, 1968 France ..l72389 [52]US. Cl. ..425/275, 423/DIG. 3 [51] Int. Cl. ..B29c 13/00 [58]fieldofSearch ..l8/2K,2S,5.5,14R,14G,

18/24, 34 S, 38, 41, 46, DIG. 3, 27, 29

[56] References Cited UNITED STATES PATENTS 2,605,505 8/1952 Ruhland..l8/4l 2,867,847 1/1959 Miller et al. 1 8/41 1,791,060 2/1931 Keen3,496,610 2/1970 Shelby et al. 18/41 FOREIGN PATENTS OR APPLICATIONS1,007,034 2/1952 France ..l8/4l Primary Examiner-Robert L. Spicer, .lr.Attorney-Karl F. Ross [5 7] ABSTRACT A shaping mold for producingfilmlike articles by the fluidization process, this mold consisting of acompletely closed enclosure formed in a metallic material having goodheat-conducting properties but a reduced thickness. The enclosurecommunicates with the surrounding free atmosphere, during the heatingthereof, via at least one tube carried by an opening into a portion ofthe enclosure which does not partake in the shaping of any portion ofthe filmlike article.

2 Claims, 4 Drawing Figures SHAPING MOLDS FOR PRODUCING FILMLIKEARTICLES BACKGROUND OF THE INVENTION This invention relates to shapingmolds for producing filmlike articles by the so-called fluidizationprocess.

Although a relatively old discovery, fluidization processing (i.e.,processing a solid in such a form that it can be handled as a fluid) wasnot carried out on a commercial scale until about a score of years agoin the field of surface coating by using thermoplastic films.

Still more recently, a method of obtaining filmlike articles by the sameprocess was proposed, but in contrast to the early practice aiming atproducing a coating or lining, wherein the primary requirement isreliable adhesion between the support or carrier element and the film,nonadhesion is essential in the manufacture of very thin articles suchas garments, high boots, hats, book dust jackets, banknote cases, etc.

Thus in the manufacture of articles of this character the use of massivemolds consisting of the outline of the article out in a relatively thickmetal plate was advocated. To facilitate the stripping of piecescomprising projections or the like, molds have also been proposed whichhad a U-section obtained for example by folding this outline in order toorient all the projections in the same direction.

The processing consists firstly in heating the mold in an oven or stoveto a temperature ranging from about 250 C. to about 300 C., thensuddenly dipping the mold, as it emerges from the oven, into a containerin which the powdered plastic material is subjected to a turbulence inorder to cause the powder to adhere to the hot mold walls and thus melt,and eventually cooling the mold for smoothing and stripping the article.

In the case of articles such as garments, the mold constitutes a closedvessel consisting of relatively thick metal-plate elements hingedlyinterconnected to facilitate the stripping of the filmlike articles byseparating said elements.

Another proposition consisted of molds closed according to this method(as exemplified in the French Pat No. 919,852) the heating step isobtained by producing an internal circulation of a heating fluid such asoil, the enclosure being connected by adequate conduits to a circulationpump.

The applicants observed that these shaping molds did not give reallysatisfactory results and accounted for defects involving considerablefailures and rejects. In fact, considering the manner in which thesemolds are designed and constructed any homogeneous heating and coolingthereof is definitely precluded, though this constitutes a sine que nonrequirement for producing commercially sound articles.

In the case ofa shaping device consisting ofa simple outline plate, arelatively thick metal plate is necessary (for example a 4-mm. thicksteel plate) so that it can have a sufficient mechanical strength and aheat capacity adequate for melting the plastic powder deposited thereon.These requirements lead to a temperature rise taking about minutes inthe case of P.V.C.), a time obviously too long for an economicalalternate operation of molds of this type.

This inconvenience is further aggravated by the fact that the least aircurrent occurring during the transfer of the shaping tool from the ovento the bath (which air current may affect both faces of the outline willcause a wavelike propagation ofa cooling effect detrimental to thetemperature homogeneity and therefore to the regularity of the filmthickness, in that it is attended by clear zones and by a poorsmoothing.

Hinge-type shaping molds seemed to constitute a definite improvement inthe art since the accidental cooling could affect only the outer facethereof, i.e., the only face likely to receive the air current; however,the applicants found that when the mold was dipped into the fluidizedbed its temperature was not sufficiently homogeneous, so that the samedefects as those mentioned hereinabove in connection with outline moldswere again observed. In fact, the hot air trapped within the mold tendedto escape through all the joints,

notably at the hinges, so that these portions were kept at a highertemperature than the others, thus frequently impairing the already poorheat distribution in the mold.

Heating by oil circulation leads to a poor economical efficiency of theproduction process. for the heating and cooling phases are excessivelylong.

SUMMARY OF THE INVENTION The present invention relates to a novel typeof shaping molds for the purpose set forth hereinabove, but free of theinconveniences of prior art devices of this character.

The mold according to the present invention is basically characterizedin that it consists of a completely closed enclosure made of arelatively thin material having a good heat-conductivity, said enclosurecommunicating with the external free atmosphere, during the heatingthereof, through at least one tube carried by and opening into a portionof the enclosure which does not partake in the shaping of any portion ofthe filmlike object.

According to a specific feature characterizing this invention, said tubeis provided with a valve.

According to another embodiment of invention, said enclosure comprisesat least two tubes, each tube having a valve inserted therein, one valvecontrolling the outward flow of hot air and the other the inward flow ofcold air.

DESCRIPTION OF THE DRAWING The attached drawings illustratediagrammatically by way of example the manner in which the presentinvention may be carried out in practice. In the drawings:

FIG. 1 is a perspective view of a mold according to the invention;

FIGS. 2 and 3 are detail views showing in a section projections to beformed on filmlike articles; and

FIG. 4 is a sectional view showing another embodiment of a shaping moldaccording to this invention.

SPECIFIC DESCRIPTION As shown in the drawing, the shaping mold accordingto this invention consists of a completely closed vessel or enclosure Creproducing the shape of the object or article to be made, theprojections of this object being obtained by means of internal orexternal appendages such as A and P, secured to the mold C. The walls ofthis enclosure and of these appendages A and P are obtained by usingvery thin sheet metal (for example having a thickness of 0.5 to 0.6millimeter). The rigidity of the shaping mold is obtained by usingbottom elements such as F. Slots D interconnect the inner space of themain shaping body with the inner space of each appendage, so that aircan circulate freely throughout these inner spaces. In fact, theapplicants found that if the appendages such as P (in this example forforming a pocket in a garment) or B (in this case a button) were formedsimply by means of a solid, massive element (such as a cutout plate or aturned element), these elements had necessarily a heating capacity otherthan that of the enclosure-forming material, due to the difference inthe thicknesses and or nature of the metal, so that the inconvenienceslisted hereinabove were observed again, with the additional drawbacks ofthe resulting projections in comparison with the main body of thearticle.

In contrast thereto, as can be seen in FIGS. 2 and 3, all theappendages, including appendages B, are made of sheet metal of samenature and thickness as the main body of the enclosure, and formed witha double wall connected to the main body on either side of the slot D bya weld seam S constituting a fillet facilitating the strippingoperation.

To afford convenient handling, the bottoms F are provided with legs orhandles such as G] and G2.

As already explained hereinabove, the air contained in the shaping moldsspreads into the inner space of the main body and also into inner spacesof the ancillary enclosures of the appendages. It will be readilyunderstood that if these enclosures were closed completely the expansionof the air contained therein, as a consequence of the temperatureincrement (up to and above 300 C. would lead to a distorsion of theseenclosures and make the shaping mold useless.

To avoid this distorsion the tube T is secured to one of the bottoms, sothat the hot air can remain at the atmospheric pressure without causingthe escape of this air to overheat certain parts as in the case ofleaks"observed in so called hinged molds. Thus, without displaying any of theabove listed inconveniences, the shaping mold according to thisinvention has all the advantageous features of the same molds, that is,the possibility of utilizing the accumulation of internal hot air as anadditional heat reserve maintaining the wall of the enclosures at auniform temperature by simple conductivity.

In certain cases it may be advantageous to provide the tube T with avalve or any other means adapted to cut off when necessary the fluidcommunication between the inner space and the surrounding medium. Thiscutoff device may consist for example of a gaged valve becomingoperative when, as a consequence of temperature, the pressure within theenclosures attains a predetermined maximum permissible value. If desireda plurality of tubes T each controlled by adequate valve means may becontemplated, some of the valves permitting the ingress of air into theenclosures and other valves permitting the exhaust of air therefrom. Theair-inlet tube T may be used for introducing a cold fluid (for instanceair) into the enclosure during the step following the smoothening step,in order to accelerate the cooling of the shaping device to thetemperature permitting the stripping therefrom of the film constitutingthe manufactured object or article.

Considering FIG. 4, it will be seen that in the inner space of enclosureC there are disposed a pair of blind appendages A1, A2 retained thereinfor example by means of distance-pieces H, the inner space of theseappendages communicating freely with the exterior via orifices 0!, 02also adapted to be used for introducing the plastic powder into thisspace and discharging any excess powder therefrom. The hot valve Vh andcold valve Vc are also shown in this figure.

Of course, various modifications and variations may be brought to thespecific forms of embodiment shown and described herein withoutdeparting from the spirit and scope of the invention set forth in theappended claims.

What is claimed as new is:

l. A shaping mold for producing filmlike articles, comprising a closedhollow body of a uniform wall thickness having surfaces adapted to bedisposed in a fluidized bed of thermoplastic particles and to be heatedto a temperature in excess of the flow temperature of the thermoplastic,and at least one bottom element other than said surfaces; a plurality ofappendages projecting from said surfaces and of a wall thicknessapproximately equal to that of said body, said appendages being hollowand communicating with the interior of said body, said body and saidappendages having a wall thickness of the order ofO.5 to 0.6 millimeter;and at least one duct connected to said body and open to the atmosphere,said duct being joined to said body at said bottom element.

2. The mold defined in claim 1 wherein two ducts communicate with saidbody at said bottom element, said mold further comprising respectivecontrol valves in said ducts for regulating the flow of hot air fromsaid body and the flow of cold air to said body respectively, said bodyand said appendages being composed of metal and said appendages beingsecured to said surfaces by weld fillets facilitating the stripping ofthe film from said surfaces.

1. A shaping mold for producing filmlike articles, comprising a closedhollow body of a uniform wall thickness having surfaces adapted to bedisposed in a fluidized bed of thermoplastic particles and to be heatedto a temperature in excess of the flow temperature of the thermoplastic,and at least one botTom element other than said surfaces; a plurality ofappendages projecting from said surfaces and of a wall thicknessapproximately equal to that of said body, said appendages being hollowand communicating with the interior of said body, said body and saidappendages having a wall thickness of the order of 0.5 to 0.6millimeter; and at least one duct connected to said body and open to theatmosphere, said duct being joined to said body at said bottom element.2. The mold defined in claim 1 wherein two ducts communicate with saidbody at said bottom element, said mold further comprising respectivecontrol valves in said ducts for regulating the flow of hot air fromsaid body and the flow of cold air to said body respectively, said bodyand said appendages being composed of metal and said appendages beingsecured to said surfaces by weld fillets facilitating the stripping ofthe film from said surfaces.